In the vicinity of La Rochelle and Rochefort, twenty kilometres from the Island of Ré and five from the Island of Oléron, the Island of Aix was long a strategic military stronghold. But it was Napoleon, rather than warfare, which made it famous. The Emperor stayed there after the Battle of Waterloo, from 9 to 13 July 1815, when he surrendered to the English. The house he stayed in was given to the nation as a museum in 1933 and now has a collection of Napoleonic souvenirs, and also an African museum.
The museum on google maps: